1. Field of the Invention
The invention relates to focal plane array signal processing. and, more particularly, to a digital offset correcting signal processor for a microbolometer focal plane array.
2. Discussion of the Related Art
A focal plane array that uses an array of radiation sensors typically suffers from variations in sensor element output from sensor to sensor. This variation comprises two basic components, an offset uniformity error and a gain uniformity error. Offset uniformity error may be measured by blocking external radiation from the radiation sensing elements of the array and measuring the variations in output from each sensor element. Gain uniformity error may be measured by presenting a uniform radiant field to the focal plane array and noting the variations in sensor element output.
Until the present invention, focal plane array offset correction has been limited to analog circuits that attempt to subtract a real time or stored analog signal from a detected signal. Such approaches provide poor offset compensation in relation to the accuracy of the apparatus and method of the present invention for providing offset correction.
One such type of radiation sensor is a bolometer. A bolometer absorbs infrared radiation. A bolometer has a large temperature coefficient of resistance and, as a result, absorbed radiation changes the temperature of the bolometer and, therefore, the bolometer's resistance. Bolometer imaging systems are sensitive to long wave infrared, typically in a wavelength range of 8-12 micrometers. Such infrared systems form images from variations in the amount of radiation emitted from objects within a field of view.